At the mid-point of my academic career, I have been productive in patient-oriented research, as documented by publications in a number of prominent journals, evidence of national and international recognition, and a good funding record from the NIH and other funding sources. My Epidemiology Research Laboratory does clinical epidemiology research in the health outcomes of human retroviruses human T-lymphotropic virus types I and II (HTLV-I and -II), and my NIH R01-funded multicenter HTLV cohort study forms the centerpiece of the Research Plan in this application. I also study the epidemiology of transfusion-transmitted viruses and of blood donor demographics and donation behavior. My current research environment includes both the UCSF Departments of Laboratory Medicine and Epidemiology & Biostatistics, my academic home, and Blood Centers of the Pacific (BCP), a community blood bank 1 mile from the UCSF campus where my Epidemiology Lab and close collaborators are located. Letters from the heads of these institutions support my K24 application, and document the strong affiliations in research and training between UCSF and BCP. I have already mentored a number of graduate students and postdoctoral researchers, as well as several professionals seeking additional training in clinical epidemiology research. I am applying for a K24 grant at this point because I would like to reduce my effort on clinical duties and specific funded projects in order to pursue new interests in patient-oriented research and to expand my mentoring activities. The new trainees would carry out supervised epidemiology research projects in HTLV clinical outcomes, in transfusion transmitted viral infections, or a new area in the epidemiology of blood donor demographics and donation behavior. They will participate in the Training in Clinical Research courses given by the UCSF Department of Epidemiology and Biostatistics. Finally, I shall expand an existing training program in International Transfusion Safety organized by BCP under an NIH Fogarty International Center grant. This program brings blood bankers from less developed countries for an intensive summer training program in research methods related to blood safety.